SGK1 up-regulates Orai1 expression and VSMC migration during neointima formation after arterial injury

B Walker-Allgaier, M Schaub, I Alesutan… - Thrombosis and …, 2017 - thieme-connect.com
B Walker-Allgaier, M Schaub, I Alesutan, J Voelkl, S Geue, P Münzer, JM Rodríguez, D Kuhl
Thrombosis and Haemostasis, 2017thieme-connect.com
Neointima formation following vascular remodelling requires complex, incompletely
understood cellular signalling in inflammatory cells and vascular smooth muscle cells
(VSMC). Vascular injury from intimal lesions in atherogenesis or after percutaneous arterial
balloon angioplasty result in vascular inflammation as well as inflammation-triggered VSMC
migration toward the vascular lumen (1, 2). Migration of VSMCs leading to neointima
formation with restenosis is mainly triggered by cytokines or growth factors such as Platelet …
Neointima formation following vascular remodelling requires complex, incompletely understood cellular signalling in inflammatory cells and vascular smooth muscle cells (VSMC). Vascular injury from intimal lesions in atherogenesis or after percutaneous arterial balloon angioplasty result in vascular inflammation as well as inflammation-triggered VSMC migration toward the vascular lumen (1, 2). Migration of VSMCs leading to neointima formation with restenosis is mainly triggered by cytokines or growth factors such as Platelet-derived growth factor (PDGF) released from inflammatory cells (1, 3). Recent findings indicate that phosphatidylinositol 3-kinase (PI3K) dependent signalling plays an essential role in VSMC migration and neointima formation in vivo (4, 5), but downstream signalling targets remained hitherto ill-defined. Targets downstream of PI3K signalling include the serum-& glucocorticoid-inducible kinase-1 (SGK1), a serine/threonine kinase that is induced by a variety of triggers, such as hyperglycaemia, oxidative stress, or ischaemia and plays a major role in several cardiovascular diseases as arterial thrombosis, vein graft stenosis, pulmonary hypertension or cardiac fibrosis (6–9). Nevertheless, the role of SGK1 in arterial neointima formation after vascular injury as well as underlying cellular mechanisms involved in SGK1-dependent arterial vascular remodelling have not been examined so far. Recently, we could show that SGK1 plays an important role in vascular inflammation, macrophage migration and matrix metalloproteinases (MMP) formation underlying atherogenesis (10). We could further show that SGK1 is a critical regulator of Orai1 (Ca2+ release-activated Ca2+ channel moiety 1, CRACM1) and of Orai1-dependent store operated Ca2+ entry (SOCE) in platelets as well as Ca2+-dependent platelet activation and thrombus formation with consecutive vascular occlusion (6, 11, 12). Since Orai1-mediated SOCE is essential for PDGF-induced VSMC migration and neointima formation (13–15), we aimed to determine the role of SGK1 for intracellular signalling in VSMC as well as VSMC-driven neointima formation after arterial injury. To this end, we generated ApoE/SGK1 double knockout mice (apoe-/-sgk1-/-) as described previously (10). Following treatment with cholesterol-rich diet (0.25%) neointima formation was induced in eightweek-old ApoE-deficient SGK1 wildtype (apoe-/-sgk1+/+) or knockout mice (apoe-/-sgk1-/-) as described previously (1, 16–19). As illustrated in▶ Figure 1 A, neointima formation in carotid arteries four weeks after vascular injury was significantly reduced in apoe-/-sgk1-/-mice compared to apoe-/-sgk1+/+ mice while media thickness was unaffected by SGK1 deficiency (see Suppl. Figure 1, available online at www. thrombosis-online. com). As revealed by immunohistochemistry, vascular inflammation represented by vascular infiltration of Mac-3+ macrophages (▶ Figure 1 B) was significantly diminished in apoe-/-sgk1-/-mice compared to apoe-/-sgk1+/+ mice. Furthermore, impaired neointima formation was paralleled by a significantly abrogated infiltration with α-SMA positive VSMC in apoe-/-sgk1-/-mice compared to apoe-/-sgk1+/+ mice (▶ Figure 1 C). To examine whether decreased vascular VSMC infiltration could have resulted from a diminished ability of VSMC to migrate we analysed migration of aortic VSMC cultivated from sgk1-/-mice or sgk1+/+ littermates towards a PDGF gradient in vitro (Boyden chamber model). PDGF occurs in all resident cells of the arterial vessel wall and its expression increases during vascular injury and atherosclerosis (3, 13). In VSMC, the pro-migratory agonist PDGF induces …
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